1. Field of the Invention
The present invention relates to a method of manufacturing foamed and molded asphalt/urethane products. More particularly, it relates to molded products most suitable for sound-proof structures for cars, for example. Still more particularly, it relates to a method of manufacturing molded products most suitable for sound-proof structures for cars used as the dash board, floor panel, in the tire house and rear baggage chamber of the cars to shield any sound coming from outside and generated from the car body panel, said products being made flatter at their surface. It also relates to laminated structures including the molded products and manufactured according to the method.
2. Prior Art
FIG. 2 shows one of the conventional sound-proof structures for cars. As shown in FIG. 2, the conventional sound-proof interior material has a simple structure comprising an acoustical layer and a sound insulation layer. A vibration control material 20 which is usually a sheet of asphalt is closely stuck to the car body panel 10. Numeral 30 represents the acoustical layer made of flat felt or the like. Numeral 40 denotes the sound insulation surface layer, which is a carpet lined with a thermoplastic resin layer to enhance its sound insulation and molding capacities when it is used as the floor insulator. The acoustical layer 30 add the sound insulation surface layer 40 are stuck each other by the common sticking means or the like.
FIG. 3 is a sectional view showing another conventional sound-proof structure for cars, which is used as the dashboard insulator. The vibration control material 20 which comprises a sheet of asphalt or the like is welded to the car body panel 10. It is often found that felt is used as the acoustical layer 30 and that a sheet of PVC (polyvinyl chloride) or the like is used as the sound insulation surface layer 40. The acoustical layer 30 and the sound insulation surface layer 40 are also stuck each other by the common adhering means or the like in this case. In any case where it is used as the dashboard or floor insulator, the vibration control material 20 consisting of asphalt sheet or the like is intended to deal with vibration, and the sound insulation surface layer 40 consisting of carpet, asphalt sheet or the like combined with the acoustical layer 30 is used as the sound insulation structure.
In the case of these conventional sound-proof structures for cars, however, the vibration control material of asphalt used to control the vibration of the car body panel is different in function from the insulator of felt combined with carpet or PVC sheet to insulate sounds. They are therefore processed independently on the car assembly line, thereby increasing the number of processes on the assembly line.
The vibration control material of asphalt is cheap but heavy and it is not sufficinntly welded to the vertical wall such as the dashboard panel.
The acoustical material of felt or the like cannot be molded to sufficiently meet any unevenness of the car body panel. As the result, its sound-proofness cannot be sufficient and it cannot be made flat at its surface. Appearance and feeling in the viewpoint of its flatness cannot be kept high in quality, particularly when it is used as the floor insulator.
Those car body panel portions to which it is difficult to weld or stick the vibration control material cannot be made sufficiently sound-proof when only the acoustical material of felt or the like and the sound insulation surface layer are used.
In the case of the conventional sound-proof structures for cars, it is asked to deal with "discomfort sounds" transmitted into the car room. In the case of those structures shown in FIGS. 2 and 3, the following manners are well known to enhance their ability of shielding those sounds whose frequencies are lower than 500 Hz, for example, and to reduce noises in the car room:
(1) Making the vibration control material of asphalt type thicker, PA1 (2) making the acoustical layer thicker, and PA1 (3) making the sound insulation surface layer heavier. PA1 (1) melting asphalt in soft urethane having successive foams, immersing the soft urethane with the melted asphalt, and drying it, or immersing soft urethane, which has successive foams, with water base emulsion of asphalt and drying it, or immersing soft urethane, which has successive foams, in solvent-solved asphalt solution and drying it (which will be hereinafter referred to as immersion manner); PA1 (2) reacting hydrophilic polyether polyol (which includes ethylene oxide more than 15%) with organic isocyanate to produce urethane polymer and reacting and foaming the thus-produced urethane polymer with water base emulsion of asphalt (which will be hereinafter referred to as foaming manner A); PA1 (3) previously solving and blending asphalt in polyol such as polybutadiene polyol which is solvable with asphalt, and mixing and foaming it with organic isocyanate, catalyst, foaming agent and the like (which will be hereinafter referred to as foaming manner B); and PA1 (4) previously reacting polyalkylene polyol of polyether type, which is not solved with asphalt, with organic isocyanate to produce urethane polymer, solving asphalt with it, and mixing and foaming it with catalyst, foaming agent and the like (which will be hereinafter referred to as foaming manner C).
When the manners (1) and (3) are employed, however, car weight is increased and efficiency of fuel is made lower. Even when the manner 2) is used, room space in the car is made smaller.
On the other hand, cars are asked these days to have higher and higher sound-proof and vibration control abilities. In addition to proposing the above-described layer structures, therefore, various kinds of materials themselves which can be used to form these layers have been discussed and proposed in relation totthese layer structures.
As one of these proposals, foamed urethane is immersed with asphalt or asphalt is added at the time of foaming urethane to form the foamed asphalt/urethane product. These products have good sound-proofness and damping characteristic.
Each of these products are supplied as a flat sheet and they cannot completely fit the unevenness of the car floor, dashboard or the like, thereby worsening their sound-proof and vibration control abilities so much
The conventional method of manufacturing foamed asphalt/urethane products includes:
However, any of the above-mentioned manners is intended for the manufacture of foamed slabs and when molding is done using these manners, the following problem are caused. Molding is impossible when the immersion manner is employed. When the foaming manner A is used, products thus molded contain a lot of water. When they are thick as a product, therefore, their drying takes a long time and their dimension stability is poor because they contract remarkably when they are dried. In addition, they are humidified and swelled because of hydrophilic polyol used. They are not therefore practical. When the foaming manner B is employed, specific polyol used is expensive and curing of products thus manufactured is unpractically slow at the time of their molding. When the foaming manner C is employed, polyalkylene polyol used is more common than those used in the foaming manners A and B and it can therefore make the cost cheaper but the foaming stability and curing of the product thus manufactured are not good. In addition, contamination of asphalt is caused at the molding process. The product produced according to the foaming manner C is therefore impractical.